Load bearing structure

ABSTRACT

The invention relates to a bearing structure for civil construction wherein light weight, longitudinally elongated bodies comprise an external layer of carbon fiber impregnated with epoxy; the bodies resin have a porous plastic core and are magnetically coupled to cooperating pairs of male and female constraining elements.

[0001] The present invention concerns bearing structures.

[0002] The invention is particularly suitable for civil structures, for instance buildings, bridges and outdoor structures exposed to weather. In known construction practice it is very common to use steel beams or concrete, mostly reinforced by means of reinforcing bar grids. Such structures typically are heavy and labor intensive.

[0003] A main object of the present invention is to provide a novel load bearing structure which is of lighter weight than reinforced concrete and has better load bearing characteristics.

[0004] Another object of this invention is to enhance the ability of a civil structure to withstand “destabilizing forces” such as earthquakes, floods, river overflows, and other odd weather events.

[0005] A further object of the present invention is to provide a light weight bearing structure which is easier and faster to assemble than the conventional bearing structures.

[0006] The above and other objects, as will appear hereinafter, are obtained with a bearing structure for civil construction featuring elongated bodies comprising at least one layer of carbon fiber impregnated in at least an epoxy resin.

[0007] Advantageously, the elongated bodies comprise an inner core made of porous plastic filling an inner space defined by an outer layer of carbon fiber. Additionally, the plastic material is an open cell structure, such as a preferable honey-comb structure. Additional characteristics and advantages of the present invention will appear more clearly from the detailed description of the preferred embodiments herein described and illustrated in the attached drawings in which:

[0008] FIGS. from 1 to 3 are perspective views of structural members according to the present invention;

[0009]FIG. 4 is a perspective view of a joint between pillars and horizontal beams according to present invention;

[0010]FIG. 5 is a perspective view, partially exploded, of the joint shown in FIG. 4;

[0011]FIG. 6 is an enlarged view of the joint shown in FIG. 4, with portions shown in section;

[0012]FIG. 7 is a top plan view of the lower pillar in the joint area shown in FIG. 4; and

[0013]FIG. 8 is a perspective exploded view looking upwardly from the bottom of the joint area shown in FIG. 4.

[0014] With reference to the aforementioned Figures, a bearing structure for civil support systems comprises a plurality of longitudinally elongated bodies 10 featuring, for instance, a poly-line cross section such as square, rectangular, T-shape, H, I or L shaped similar to cross sections typically used in metal beam structures presently used in civil construction.

[0015] Each one of the longitudinally elongated bodies 10 comprise at least an outer layer of carbon fiber 11 impregnated with epoxy resin. The carbon fiber fabric can be manufactured with strands described in the patent application PD 2000A5 filed in Italy on Jan. 13, 2000 teaching that the strands are formed of a plurality of yarns out of which at least one is metal (wire) and at least one other is a carbon fiber yarn. The strand of the carbon fiber fabric may also comprise ceramic yarn. For the impregnating epoxy resin, which also acts as glue, a readily available resin polymerizing at room-temperature may be used, for instance resin manufactured by CIBA-GEIGY in USA.

[0016] Alternatively, a resin polymerizing at a temperature higher than room temperature can be used in cases where a heating chamber is available. The longitudinally elongated bodies 10 comprise a core 12 of porous plastic, for instance a foamed resin, which fills the internal cavity defined by the outer layer 11 of carbon fiber. A honey-comb open cell core structure is preferred.

[0017] The manufacturing process, to provide an example, employs a steel mold (pattern) on which a layer of impregnated carbon fiber 11 is applied according to the traditional manufacturing process used for carbon fiber. Once the carbon fiber layer becomes solid and the steel mold (inner pattern) removed, the outer layer (skin 11) is filled with the core 12 that, once polymerized, becomes totally adherent to skin 11 thus forming structural continuity that allows the bodies 10 to withstand mechanical stresses, particularly vibrations. It is important to observe that the number of layers 11 for each longitudinally body 10 is proportional to the load that the beam is to bear. In bodies 10 used for building, the number of layers 11 can be less for the beams dedicated to the upper floors versus the ones dedicated to the lower floors because of the load differences.

[0018] According to the present invention, each body 10 extremity comprises co-operating constraining elements, male 13 and/or female 14, which are complementary to one another in forming a connector joint, for instance between beam and pillar when the bodies 10 serve such functions (see FIGS. 4 to 8 beam 10 a and the pillar 10 b).

[0019] The constraining male element 13 comprises a cap 15 which is a permanent magnet preferably shaped as a hemisphere, integral with or applied to a pillar body 10 b (for instance by means of a restraining joint 18 or by adhesives), positioned on the upper end of 10 b and of a number equal to the number of beams 10 a to be engaged. FIGS. 4 and 5 show caps 15 arranged as a cross because four beams 10 a are connected to pillar 10 b. It is also noted that the restrained joint 18 (see FIG. 6) features a backlash clearance to accommodate minor structural movements (see arrows 22).

[0020] The constraining female element 14 comprises a body 16, integral with or applied to the beam body 10 a and shaped in mirror relation to cup 15 with a concave surface, defined by a layer 17, made of magnetic material such as iron, in order to provide retention force with the permanent magnet of cup 15. In this way, a positive constraint between beam 10 a and pillar 10 b is achieved which can be built suitable for limited movements of the spherical members (see arrows 19 and 20 in FIG. 4 and the dotted line 21 in FIG. 6) which movement is regulated as desired by simply modifying the size or the material of the permanent magnet to consequently change the attraction force of the connection.

[0021] It is contemplated that the shape of the constraining elements 13 and 14 instead of hemi-spherical could be disc-like or the female element located on the pillar head 10 b and the male element on the beam 10 a. A body 10, such as in the case of pillar 10 b, can be equipped with its head portion free from the male constraining elements 13, (center and corner areas) while elements 13 a, of the same kind may comprise a magnetic cup, dedicated to receive another pillar 10 c featuring female constraining elements 14 a as aforementioned (see FIG. 8).

[0022] It is thus shown how the present invention reaches its desired goal. The calculation (summarized in the table below) of the bearing capacity of a pillar loaded with a combined bending and compressive stress, clearly shows the advantage in terms of bearing capacity as well as weight of a beam manufactured according to the present invention (square cross section, 200 mm×200 mm, layer 11 thickness of 4 mm, epoxy resin as a core) versus a reinforced concrete beam having the same cross section (200 mm×200 mm) and built with the best concrete (which according to industry standard is 450 Kg/cm2)and reinforced with 20% of steel re-bars offering a 400 Mpa (400 MegaPascal=specific resistance like Lbs per square inch). Re-bar Carbon Resin Concrete (Steel) fiber total total total cross cross cross cross section section section section Load (Al) (Al) (Al) (Al) Weight Capacity Cm2 Cm2 Cm2 Cm2 Kg/m Kg Carbon 31.36 368.64 49.568 1.172.480 Fiber (1) (3) Pillar Reinforced 320 80 208 464 concrete (2) (4) Pillar Performance 23.83 252.69 difference Resisting 80 kg/mm2 25 kg/mm2 450 kg/cm2 40 kg/mm2 strength (R1, R2, R3, R4) Weight 1.7 1.2 6.2 7.8 (D1, D2, D3, D4) kg/dm3m3

[0023] Having described this invention, it is apparent that numerous modifications can be applied to the present invention described for generating alternative embodiments, all to be considered covered under the same inventive concept. Furthermore, the components can be replaced with alternative elements. Practically, the materials used, as long as technically equivalent, as well as dimensions, can be according to the application needs. 

What is claimed:
 1. Bearing structure for civil constructions, wherein longitudinally elongated bodies comprise at least one outer layer of carbon fiber fabric impregnated by at least one epoxy resin;
 2. Structure according to claim 1 wherein said longitudinally elongated bodies comprise a porous plastic core filling the space bounded by said at least one outer layer of carbon fiber.
 3. Structure according to claim 2 wherein said plastic core is characterized by a porous, open-cell structure.
 4. Structure according to claim 2 wherein said plastic core has a honey-comb structure.
 5. Structure according to claim 2 wherein said core is an epoxy resin.
 6. Structure according to claim 1 wherein said at least one outer layer of carbon fiber fabric comprises strands in which at least one is a metal wire and at least one is a carbon fiber yarn.
 7. Structure according to claim 1 wherein the carbon fiber fabric comprises ceramic yarns.
 8. Structure according to claim 1 wherein said impregnating epoxy resin acts as glue and is polymerized at room temperature.
 9. Structure according to claim 1 wherein said impregnating epoxy resin is a resin polymerized at a temperature higher then room temperature.
 10. Structure according to one any of the above claims wherein said longitudinally elongated bodies comprise constraining elements male and female, complementary to one and other located at outer ends of said bodies.
 11. Structure according to claim 10 wherein one of said male constraining elements comprises a permanent magnet cap, which is solid with or applied to a related longitudinally elongated body.
 12. Structure according to claim 11 wherein one of said female constraining elements comprises a cradle, which can be integral with or applied to a related longitudinally elongated body, said cradle being mirror shaped to mate with said cap and having a convex surface defined by a layer of material magnetically attracted to the permanent magnet of said cap.
 13. Structure according to one or more of claims 10 and 12 wherein said cap as well as said cradle are of hemispherical shape.
 14. Structure according to claim 10 wherein said male and female constraining elements are connected to longitudinally elongated bodies by means of dove-tail constraints and glue.
 15. Structure according to claim 10 wherein said male and female constraining elements are connected to longitudinally elongated bodies in a way that allows transactional settlement movements of said male and female elements. 